﻿Manchester Memoirs, Vol. xlix. (1904), No. IV 5 



strongly, but beyond this nothing but a trace of a 

 continuous spectrum appeared on the photographs. I 

 concluded that the failure was due to insufficient reflection 

 of the short waves from the surface of the grating. 



The only chance of success seemed to lie in using a 

 transmission grating ruled on some transparent substance. 

 Through the generosity of Mr. Hans Hauswaldt, of 

 Magdeburg, this was made possible. 



A plane-grating having 500 lines per mm. was ruled 

 by Rowland on a plate of transparent fluorspar of 4 cms. 

 edge, and J cm.. thickness. 



A vacuum spectrograph, similar to the one used by 

 Schumann, was built for Mr. Hauswaldt by Fuess, of 

 Steglitz. The camera and slit were exact reproductions of 

 the corresponding parts of Schumann's apparatus, but the 

 body of the instrument was modified to suit the method 

 of using the grating. Fig. 2 is an outline of the design of 



Thc Hauswaldt 

 Spectrograph 



Camera 



Fig. 2. 



the apparatus. The collimator and camera tube were 

 fixed relative to one another at a small angle, and the 

 grating could be rotated and its position read off by 

 means of two verniers on a graduated circle attached 

 to it. 



The slit could be adjusted, and the collimating and 

 focussing lenses racked out without disturbing the 

 vacuum. 



The plate-holder could be raised, enabling ten photo- 

 graphs to be taken on one plate, without admitting any 



